XML 87 R80.htm IDEA: XBRL DOCUMENT v2.4.1.9
Note 7 - Stock-based Compensation (Details) - Nonvested Performance Share Units (Performance Shares [Member], USD $)
In Millions, unless otherwise specified
 12 Months Ended
Dec. 31, 2014
Granted in 2012 [Member]
  
Note 7 - Stock-based Compensation (Details) - Nonvested Performance Share Units [Line Items]  
Accrued $ 8us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent
/ us-gaap_AwardDateAxis
= gas_GrantedIn2012Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Maximum aggregate payout 20gas_MaximumAggregatePayout
/ us-gaap_AwardDateAxis
= gas_GrantedIn2012Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Granted in 2013 [Member]
  
Note 7 - Stock-based Compensation (Details) - Nonvested Performance Share Units [Line Items]  
Accrued 7us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent
/ us-gaap_AwardDateAxis
= gas_GrantedIn2013Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Maximum aggregate payout 21gas_MaximumAggregatePayout
/ us-gaap_AwardDateAxis
= gas_GrantedIn2013Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Granted in 2014 [Member]
  
Note 7 - Stock-based Compensation (Details) - Nonvested Performance Share Units [Line Items]  
Accrued 4us-gaap_DeferredCompensationSharebasedArrangementsLiabilityCurrentAndNoncurrent
/ us-gaap_AwardDateAxis
= gas_GrantedIn2014Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember
Maximum aggregate payout $ 24gas_MaximumAggregatePayout
/ us-gaap_AwardDateAxis
= gas_GrantedIn2014Member
/ us-gaap_AwardTypeAxis
= us-gaap_PerformanceSharesMember